QUALITATIVE Torque calculation 3

[Alfninux]

Hi everyone. I've a question related to the QUALITATIVE computation of the required torque to make a rotation.

The image shows a cross section. Two rigid bodies (hollow cylinder and elliptic base cylinder) and a deformable element are shown.
Supposing to know all the mechanical properties required, how do I compute (qualitatively) the torque required to make a 90deg rotation of the inner elliptic body in order to deforme the deformable element?

The deformable body and the outer cylinder are linked along their contact surface, and cannot slide

 

[Alfninux]

Brian Petersen. Based on your experience. What do you advise?

 

[BrianPetersen]

Build it (out of steel and rubber or whatever you choose for that odd-shaped internal bushing). Test it.

 

[CWB1]

The various solvers built into the 3d modelers today are fairly simple to use and surprisingly accurate within the elastic range of materials, I'd start there. A lot of folks new to simulation get caught up in solving for a single solution then gripe about a lack of model accuracy vs reality. What you should always start with in simulations is to run sweeps and document the impact of variables on the final result so you understand what factors are significant vs not. As a mentor of mine once told me, its not about the number but rather the trend. Once you understand the trend, getting to the correct values is simple.

 

[Alfninux]

Which STEP should I use to run it on ABAQUS? Dynamic,Explicit?

 

[Alfninux]

I want to impose a motion to the internal bushing (angular motion 0° to 90°). In a given angle it touches and then deforms the "deformable element" until it reaches the desired 90° rotation. I would like to get the required torque to perform that motion. What kind of analisys should I perform on Abaqus?

 

[rb1957]

and so we come full circle (you've restated the original post).

We've (generally) advised using reale world testing but you persist with trying to model this.

 

[FEA way]

You can use Abaqus/Standard (Static General or Dynamic Implicit analysis) or Abaqus/Explicit. All should give your results. However in this case I recommend Explicit since high deformations are expected and general contact algorithm will be very useful. Explicit won't have convergence issues but keep in mind that it may take a lot of time to solve. Thus try artificially reducing time step.

 

[BrianE22]

How did we get by before FEA? Put the CAM in different positions and break down the load on the rubber into axial and tangential (shearing) components. I'd think you could find some resources on the web that would give you typical stiffnesses for rubber in compression and rubber in shear. Granted your constraints aren't so simple but that is where judgment comes into play.

You want to have some idea of the loads so you can validate your FEA results. Having ball park numbers would certainly be helpful before physically building anything.